LAUSR

In 1980, the compositions of a set of microbeam reference materials were published [1] and made available to the world. These mostly mineral and natural glasses were characterized by classical wetchemical analysis by staff of the Department of Mineral Sciences of the Smithsonian Institution (SI) and named the Smithsonian Microbeam Standards (SMS). Additional carbonates, synthetic rare-earth element phosphates and trace element doped synthetic glasses were added to the collection bringing the total number of currently available samples to 57. To date more than 1300 requests have been filled with over 20,000 individual samples distributed to laboratories worldwide free of charge. Whereas a few of these are no longer available because of very limited quantity, most have quantities sufficient for distribution for many decades at the current demand in aliquots of sufficient size for electron beam microanalysis reference mounts. However, in the last ten years there has been about a threefold increase in the number of SMS distributed (see figure 1). The reason for this increase is not clear. Many requests are for labs with new instrumentation including more frequently for quantification using energy dispersive x-ray spectroscopy. More requests are also coming from laser ablation labs for which only some of the SMS are in sufficient quantity to be appropriate. Laboratories with heavily used mounts in need of replacement are encouraged to request replacement samples. The Corning glass archaeological reference samples, doped with selected trace elements, exist in reasonably large enough quantities to be suitable for destructive analytical methods.